Your TV has sound but a black screen — backlight failure

You switch the TV on, you hear the usual start-up chime, a channel is talking or music is playing — but the screen stays black, or so dim you can only make out a picture by leaning in close. This is one of the most common cases we see on the bench, and it almost always means one specific thing: the panel is working, the image is being built, but nothing is lighting it up anymore. The good news is that a TV like this is usually repairable, and below we show you how to confirm it yourself with an ordinary pocket torch.

The clearest sign: sound is there, screen is black (or very dim)

Let's start with what is actually happening. In an LCD or LED TV the picture is formed by the panel, but it is lit from behind by a separate LED backlight system — strips of LEDs mounted along the edges of the panel or behind it. These are two completely separate parts. If the backlight is not lit, the panel keeps working — it still builds the image, decodes the signal and outputs sound — but all you see is black glass.

That is why the sound is such important evidence. If the TV:

• plays the start-up jingle or channel audio,
• responds to the remote (you hear the volume beep or channels changing),
• but the screen is black or only faintly dim —

then the processor, main board and panel are most likely fine. Suspicion falls on the backlight. The next step lets you confirm exactly that assumption in a minute, without opening the TV.

The torch test — backlight or the panel itself?

This is the simplest and most reliable test you can do at home, and every technician does it before opening a TV.

1. Leave the TV switched on and switch to a bright image — for example the menu screen or any channel with a bright background (not a black pause screen).
2. Darken the room so it is easier to see.
3. Take a bright pocket torch or your phone flash and hold it at a shallow angle close to the screen — about 5–10 cm away.
4. Slowly move the light across the screen and look closely directly under the beam.

What it tells you:

• A dim but clearly recognisable image under the torch (menu icons, text, a moving picture) — the panel is healthy, but nothing is lighting it. That is a backlight fault. A TV like this is repairable: usually by replacing the LED strips or the backlight driver.
• Nothing under the torch — just black glass, even though sound is playing — more often this is also the backlight, just burnt out more thoroughly; sometimes it is a panel or ribbon-cable issue. This needs diagnostics on site.
• Cracks, "ink stains" or coloured bleeds on the screen — the panel is physically damaged, and the torch test does not help here. More on this separately below.

The torch test is a typical do-it-yourself boundary: you check for yourself and confirm the image is there, but replacing the backlight already means opening the panel, and that happens on the bench.

What actually breaks in the backlight (LED strips, driver, power board)

Once the torch test confirms the panel is healthy, the next step is to find which part of the backlight is not working. In practice the problem is almost always in one of three assemblies.

LED strips. Behind the panel (or along the edges) are chains of LEDs wired into a single line. They age over time, and a single LED that breaks (opening the circuit) is enough to extinguish the whole chain. The result is either a fully black screen, or a dark band in one part of the screen while the rest still glows. This is the most common cause, and replacing the LED strips is a standard, worthwhile repair.

Backlight driver (LED driver / boost section). This is the part of the power board that "pumps" a low voltage up to a higher, stable voltage for the LED chains and keeps them lit evenly. If the driver or its protection cuts out, the LEDs are fine but simply receive no current — the screen stays black. Sometimes it shows itself as the backlight lighting up for a moment and immediately going out (the TV is "protecting itself").

Power board. Its constant-voltage line feeds both the backlight and the logic. Bulging or dried-out capacitors here are a typical culprit. This part is worn especially hard in older Riga buildings by voltage swings — more on that shortly.

All three are repairable assemblies. That is exactly why the sound-yes-picture-no case is so often solved on the bench by reasonable means rather than a panel swap.

No picture AND no menu/sound — when it is the main board or T-Con

The torch test leads down a completely different path if it turns out there is nothing at all — no image under the torch, no response to the remote, no sound, no menu.

If there is neither picture nor menu (whether or not there is sound), the backlight is no longer the prime suspect. Here the typical culprits are:

• Main board or processor — the TV does not build an image and does not respond to controls. Often only the standby indicator is left, while the screen and menu are dead.
• T-Con board (Timing Controller) — it converts the signal from the main board into a form the panel understands. If the T-Con fails, you can get a black screen, strange colour fields, or half the screen not working, even if the backlight is lit.

The simple logic we use: sound and menu, but a black screen → backlight or panel; no menu and no picture → main board or T-Con. Before carrying the TV in, it is worth trying one step at home — a full power cycle: unplug the TV from the socket for a minute, disconnect all HDMI and USB devices, and plug it straight into the socket, not through an extension lead. Sometimes that releases "stuck" logic. If it does not help, the boundary is clear — what follows is board diagnostics on the bench.

Why the backlight burns out earlier in Baltic conditions (heat, humidity, voltage)

Experience shows that backlight failures appear here in the typical 4–6 year ownership window — and local conditions speed it up.

• Dry heating-season heat. LEDs dislike heat, and a TV hung on the wall directly above or next to a radiator bakes at a raised temperature all winter. Heat is the main thing that shortens the life of the LED chains and dries out the capacitors on the power board.
• Baltic humidity and salt air. High humidity, especially in flats closer to the sea, gradually promotes oxidation on board solder joints and connectors. It does not always kill straight away, but it "eats" the contacts and makes a failure almost inevitable.
• Voltage spikes in older Riga buildings. In the wiring of older buildings the voltage "floats", and sharp spikes hit the power board and the backlight driver first. If the TV is plugged in without surge protection, this board is the one that suffers first.

It is not inevitable, but it explains why the backlight is so often the first thing to give in. A surge filter and a couple of centimetres of clearance around the TV for ventilation noticeably extend that life.

Repairable or not — LED strips versus a cracked panel

Here is the key decision that separates a worthwhile repair from a pointless one.

The key is this: burnt-out LED strips are repairable, a cracked panel is not. A physically damaged panel (from a drop, pressure or a knock) needs the whole panel replaced, which comes close to the value of an equivalent TV and so is rarely a sensible choice. Backlight repair is a completely different matter — it brings the TV back by reasonable means. That is exactly why the torch test is so valuable: it tells you at home which of these two stories you are in. For more on when a repair beats a new TV, read the article on TV repair versus replacement, and on other screen defects, the article on TV screen problems.

Symptom → cause → action

Before bringing the TV in, do two steps at home: the torch test (to know whether the panel is alive) and a full power cycle from the socket for a minute. Everything else — opening the panel, replacing the LED strips, driver or power board — leave safely to the bench. We work with Samsung, LG, Sony, Philips, Hisense and TCL TVs; we determine the specific cause and solution on site after inspection. For more on what we do, read the page on TV repair.